Lithogeochemistry

Lithogeochemistry, as used in this presentation, is defined as the determination of the chemical composition of bedrock material with the objective of detecting distribution patterns of elements that are spatially related to mineralization. Mineralogical alteration zones in host rocks around mineral deposits have long been recognized and used as indicators of ore. Such alteration zones are the visible manifestations of physical and chemical changes in the host rocks resulting from either primary reactions associated with ore formation or subsequent secondary reactions between the ore and the host rocks. Chemical alteration halos may be more intense, and therefore detectable, over greater distances than mineralogical halos, since the lattice substitution of elements may be detected chemically without having any mineralogical representation. The scale and intensity of changes in the chemistry of the host rock is a function of the genesis of the ore, the chemistry of the host rock, and the nature of the secondary processes. Appreciation of these factors is fundamental to the successful application of lithogeochemistry to mineral exploration. Lithogeochemistry has application at three levels of exploration: identification of geochemical provinces, favourable ore horizons, plutons or volcanic horizons on a regional reconnaissance scale; recognition of local halos related to individual deposits on a local reconnaissance or follow-up scale; and wall-rock anomalies related to particular ore-shoots on a mine scale.